The present invention relates to the alignment of optical elements, and in particular to a method of aligning optical elements with the help of a laser spot welder.
In the fiber optics industry, a recent push towards automation has forced manufacturers to rethink the standard products and processes, and consider other materials and methods that would make automation easier to implement. Conventionally, glue has been used to fix various elements used in fiber optics together. However, gluing can cause losses in signal strength, and is very difficult to automate. Therefore, the effectiveness of other attaching methods has been explored. One such alternative attaching method is welding. One of the major drawbacks with welding is that it is very difficult to align, hold and weld small elements with the precision required in the fiber optics field.
Some conventional welding machines use fork-shaped tools to hold the elements together while they are being welded. Unfortunately, these devices do not apply evenly distributed forces to the elements, which results in significant shifts during welding. This misalignment is compounded by any post-weld shift, which occurs when the molten metal contracts during solidification, resulting in the two surfaces being pulled together.
One method that has been developed in an attempt to overcome these problems is disclosed in U.S. Pat. No. 5,386,488 issued Jan. 31, 1995 in the name of Yoichi Oikawa. This method still uses a fork-shaped clamping tool to hold the elements during welding, but it overcomes some of the disadvantages of the prior art by placing a jig in between the clamping tool and one of the elements in an attempt to distribute the forces more evenly. The drawbacks in this invention include the need for a large number of welds to hold all the elements together, and the need for the specially designed jig. Each welding step could cause a minor misalignment, which would require an extra realignment step. This delay would greatly increase the cost and time of manufacture for each part. Similarly, the manufacture and application of the jig will also greatly increase the manufacturing time and cost.
An object of the present invention is to overcome the shortcomings of the prior art by providing a method that ensures good optical coupling between elements during an automated assembly process.
Accordingly, the present invention relates to a method for aligning a first optical element with a second optical element comprising the steps of:
a) securing the first optical element in a first holding means, the first optical element including a first metallic portion mounted thereon;
b) securing the second optical element in a second holding means, the second optical element including a second metallic portion mounted thereon;
c) launching an input signal through the first optical element to the second optical element, and measuring an output from the second optical element;
d) adjusting the relative position of the first and second optical elements until the output from the second optical element is above a predetermined threshold;
e) fixing the first optical element to the second optical element;
f) releasing the first or the second optical elements from the first or the second holding means, respectively;
g) applying a series of test forces to the released one of the first or the second optical element until an optimum deflection of the released one of the first or the second optical element is found, whereby the output from the second optical element is above a desired level; and
h) applying at least one weld to the first or the second metallic portion that substantially provides the optimum deflection to the first or the second optical element.